The present invention relates generally to a collar and a gravel trap assembly for an undergravel aquarium filter system and an improved undergravel filtration system for aquarium fish tanks. More particularly, the invention relates to an aquarium undergravel filtration system which has been adapted so as to prevent gravel from falling into and blocking the openings on the bottom plate of the filter system into which the uptake tubes of the filter system are placed. This adaptation involves the inclusion of a gravel trap in each opening for the uptake tubes in the bottom plate of the filter system.
Undergravel filter systems are often used in aquarium fish tanks in order to clean and purify the aquarium water by eliminating and neutralizing fish wastes, leftover food material, and other debris in the aquarium. The conventional undergravel filter system is formed by one or more bottom plates which are positioned at the bottom of a fish tank under a covering layer of the bottom material of the fish tank. The bottom material is usually in the form of gravel or small pebble mixtures. The bottom plates are provided with a multiplicity of small holes or slits which are adapted to allow the passage of water and waste material into a cavity which is formed under the bottom plates and over the bottom surface of the fish tank.
In order to function properly the undergravel filter is provided with a means to produce a current in the water of the fish tank. This current draws the water and waste material into the cavity through the bottom material covering and through the holes or slits in the bottom plate. Conventionally, in order to produce this current the undergravel filter system is provided with uptake tubes or stems with a diameter of approximately 0.5 to 1.5 inches and usually a 1 inch diameter. These uptake tubes are fitted into suitable openings in the back portion of the bottom plate. The uptake tubes or stems, when placed in the bottom plate openings form a clear passage into the bottom cavity under the bottom plate. In order to produce the required water current, a bubbling device, such as an airstone or the open end of an air supply tube is place at the bottom of the uptake tubes or stems in the interior of the tube. The bubbling device is conventionally attached to an air supply source by air supply tubing which passes into the interior of the uptake tube. The bubbles produced by the bubbling device rise through the interior space of the tube and out of an opening at the top of thetube. As the bubbles rise water is drawn along with the bubbles up the tube from the interior cavity under the bottom plates. This in turn causes water and debris to enter the cavity under the bottom plate through the slits and openings formed for this purpose. Further, the bubbling created by the bubbling device provides necessary aeration for the aquarium. In order for the the under gravel filter system to function suitably it is necessary that there be a clear passage between the interior of the uptake tubes and the bottom cavity formed by the bottom plate. It is essential that this passage be maintained free and clear of any blockages.
Often, in the operation of an aquarium which utilizes an undergravel filter system, it is necessary to remove the uptake tubes from the openings in the bottom plate in which they are positioned. When the uptake tubes are removed the gravel bottom material of the fish tank often falls into the opening in the bottom plate and passes into the bottom cavity or clogs the passage way formed by the opening in the bottom plate into which the uptake tubes are placed. This is because the gravel material covering the bottom plate of the undergravel filter system is often at a level which is near or above the point at which the uptake tube is fitted into the opening in the bottom plate. This is often the case even when the opening into which the uptake tube is fitted is provided with a collar extending above the level of the surface of the bottom plate. Collars often do not extend upward beyond the conventional depth of the gravel material. When gravel material falls into the opening provided for the uptake tube it is extremely difficult to clear the passageway for the free flow of water from the bottom cavity into the interior of the uptake tube. This causes clogging in the passageway and significantly decreases the effectiveness of the undergravel filter system in respect to the cleaning the water in the fish tank.